1. Field of the Invention
This invention relates to spring back loose leaf binders.
2. Description of the Prior Art
The closest prior patent art known to applicant consists of the following U.S. Pat. Nos.:
210,193 PA1 664,544 PA1 755,380 PA1 1,347,342 PA1 2,229,936 PA1 2,607,351 PA1 2,729,835 PA1 2,731,967 PA1 2,906,268
In addition to the above-cited prior art, is a practice in the industry (e.g., by applicant) of constructing spring back binders with asymmetrical springs in order to attain a preload condition. This prior art practice is illustrated in FIGS. 1, 2 and 2A of the drawing. Aside from the fact that the resultant pre-load is minimal -- sometimes entirely lacking -- this practice produces a disaligned binder which has the appearance of being defective.
Another practice in the industry is to construct spring back binders with symmetrical springs and to provide an inner folder for the binder which fills the gap between the opposing ends of the springs. FIG. 2B of the drawing shows a typical symmetrical spring wherein the spring arms focus upon a common line. However, it has not been found feasible to maintain the ends of the arms in contact with each other. The result is a balanced spring but with a gap between the ends of the arms. By definition, this precludes an initial or pre-load condition and, as has above been stated, this gap is sometimes filled by means of a folder which is placed within the binder.